Electromechanical device



Feb. 28, 1967 H. w. SCHAFFT 3,307,055

ELECTROMECHANI CAL- DEVI CE Original Filed Nov. 19, 1963 2 Sheets-Sheet1 flilli- I! Feb. 28, 1967 Original Filed Nov. 19, 1963 H. W. SCHAFFTELEGTROMECHANT'LICAL DEVICE 2 Sheets-Sheet 2 f 74 sounce ZZZ AM P.

' REVERB AME INVENTOR.

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United States Patent O 3,307,055 ELECTROMECHANICAL DEVICE Hugo W.Schaift, Des Plaines, Ill., assignor to Motorola, Inc., Franklin Park,Ill., a corporation of Illinois Original application Nov. 19, 1963, Ser.No. 324,638, now

Patent No. 3,281,724. Divided and this application Dec. 2, 1965, Ser.No. 511,180

9 Claims. (Cl. 3108.6)

This invention relates to devices for producing delayed decayingelectrical signals, and more particularly to a reverberation devicewhich may be used in connection with sound reproduction apparatus forelectrically simulating the acoustic conditions of a large room.

This application is a division of application Serial No. 324,638, filedNovember 19, 1963, now Patent No. 3,281,- 724, and assigned to theassignee of this application.

Certain musical performances, such as a symphony orchestra concert, aregenerally given in a large hall wherein the music will reach the ear ofthe listener via a direct path and via several other reflecting pathsthat are caused by sound waves bouncing off the walls, ceiling, andother reflecting surfaces of the hall. Numerous reflections willtherefore reach the ear of the listener in a successive order, theamplitude thereof decreasing exponentially. Because commerciallyavailable recordings or broadcasts often contain no reverberation, whensuch sound is reproduced in living room or automobile of a listener, thesmallness of the enclosure will generally preclude the occurrence of anydetectable reverberation.

It is, therefore, often desirable, in sound reproduction systems whichare used in rooms that are smaller than the rooms in which the soundbeing reproduced is normally heard, to utilize a reverberation device.Such a device will produce delayed, decaying electrical signals tosimulate the acoustical characteristics of a large room, auditorium, orconcert hall with a sound source located therein at some distance from alistener. The concert hall effect thus attained achieves a subjectiveenlargement of the room or enclosure in which the listener is located.

Numerous ways have been proposed to produce delayed decaying electricalsignals. One of those ways is to change the electrical signals tomechanical vibrations to be transmitted along a vibration transmittingpath which delays the trans-mission and produces echoes or re fiections,which are then re-converted into electrical signals for the desiredreverberation effect. Devices providing suflicient delay within areasonable range of frequencies, and providing suflicient reflectionssuch that their separate arrival times are indistinguishable by ear,have been relatively complex and expensive. Furthermore, such devicesare often excessively large and are sometimes very sensitive tovibrations from outside sources. This latter defect can be especiallyannoying in automobiles.

Accordingly, it is an object of this invention to provide an improvedreverberation device closely simulating the acoustical characteristicsof the concert hall.

Another object of the invention is to provide a compact reverberationdevice which is low in cost and simple of construction.

A further object of the invention is to provide an improved highefliciency transducer device for a reverberation unit, and a mountingfor such device wherein all but torsional vibrations are damped.

A feature of the invention is the provision, in a device for producingdelayed decaying electrical signals, of a pair of vibration transmittingmembers, each having one end connected to a transducer device and theother end suspended. A link couples vibrations between the two membersat a point intermediate their ends to provide a primary vibrational pathbetween the transducers, and a 3,307,055 Patented Feb. 28, 1967plurality of secondary paths of different lengths for reflectedvibrations.

Another feature of the invention is the provision, in a device asdescribed, of structure for suspending the ends of the vibrationtransmitting members to reflect vibrations therein in different phaserelationships.

Another feature of the invention is the provision of a transducer deviceincluding a pair of adjacent levers and an energy converting element fordisplacing a first end of each of the levers according to an electricalsignal, and for producing an electrical signal according to displacementof those ends. The levers are disposed so that the second ends move inopposite directions to produce torsional movement upon displacement ofthe first ends, and such that displacement of the second ends inopposite directions due to torsional movement causes displacement of thefirst ends.

In the drawings:

FIG. 1 is a top plan view of a accordance with the invention;

FIG. 2 is a perspective view of a portion at the upper end of the deviceshown in FIG. 1;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a perspective view of the transducer device of the invention;

FIG. 4a is a perspective view of an alternative construction for thetransducer device of FIG. 4;

FIG. 5 is a schematic showing of the transducer device of FIG. 4;

FIG. 6 is a perspective view of the transducers and connection for theright hand spring shown in FIG. 1:

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 1;

FIG. 8 is a perspective view of the mounting block for the transducershown in FIG. 4; and

FIG. 9 is a block diagram of a circuit in which a device constructed inaccordance with the invention may be incorporated.

A reverberation unit constructed in accordance with the inventioncomprises two identical torsional transducers, two helical springs ofequal length, a coupling link between the ends of the springs, and ahousing for carrying these elements. One of the transducers operates asa driving element while the other operates as a receiving element. Oneside of the first spring is connected to the driver transducer while itsopposite end is suspended in such a way as to rotate freely. One end ofthe second spring is connected to the receiver transducer while itsother end is connected rigidly to a mass. A coupling link intermediatethe ends of the springs transmits torsional vibrations therebetween.

The driving and receiving transducers are substantially identical. Thetransducers incorporate a ceramic bender or bimorph and a lever systemwhich converts the bending motion of the bimorph into a force couple.When this force couple acts upon the helical spring in the reverberationunit, it produces a torsional motion therein. The reverse is also trueso that identical lever systems are used for both input and output. Thelever system comprises a pair of levers which are fulcrumed intermediatetheir ends, and these fulcrums are fixed in relation to the center ofthe bimorph by a joining web. Each of the ends of the bimorph engages arespective one of the ends of each of the levers for displacing the sameaccording to electrical signals applied to the bimorph, or in the caseof the receiver transducer, for .being displaced according to its drivemotion to produce an electrical signal in the bimorph. The ends of thelevers opposite the bimorph move in opposite directions in response tobending of the device constructed in bimorph or in response to vibrationof the spring to which they are attached.

One means of attaching the levers to the springs is by a stainless steelextension of generally U-shaped configuration. The free sides of theU-shaped extension are attached to respective ends of the levers, andthe joining portion of the extension is connected to drive the spring.An alternative connection includes a nylon pin extending between the twolevers, the center of which is joined to the spring. The transducer ismounted in a universal mounting which is not susceptible to torsionalvibrations but which is free to move and damp out all other modes ofvibration. Further damping is provided by a mounting plate upon whichthe elements of the reverberation device are suspended, which mountingis attached to a housing which may also be damped when mounted.

Referring now to FIG. 1, a reverberation unit constructed in accordancewith the invention is shown. The unit is carried on a mounting plate 11which in turn is attached in a housing 12 by means of rubber dampers 13fixed to projections 14 of plate 11. A pair of transducers 16 and 17 aremounted on one end of the plate. The details of the transducers andtheir mounting will be described subsequently. Transducers 16 and 17 arenearly identical and may serve as either the input transducer or theoutput transducer for the reverberation unit. In FIG. 1, transducer 16is the input or driving transducer whereas transducer 17 is the pick-upor receiving transducer.

A pair of helical delay springs 20 and 21 are coupled at one end totransducers 16 and 17 respectively. As will be explained subsequently,transducer 16 imparts a torsional vibration to spring 20 which istransmitted to spring 21 and received by transducer 17. Both springs 20and 21 are identical except that they are wound in opposite directions.This is because any helix, when expanded or retracted, will produce atorsional motion, and hence springs 20 and 21 are susceptible toproducing a torsional motion by a strong shock from outside of thereverberation unit. Because the springs are oppositely wound, however,the effect of such outside vibrations is virtually cancelled out. Thenumber of turns in each spring is the same.

Referring now to FIGS. 1 and 2 the reflective means for suspending thesprings at the ends opposite the transducers may be seen. Spring 20 isprovided with a hook 22, and a length of string 23 (preferably of Dacronor some other similar durable material) is knotted to the hook 22 suchas by a girth hitch. A lead terminal 24 is mounted in an upwardlyextending flanged end 25 of plate 11, and string 23 is drawn through aslot 26 in terminal 24 to the position shown in FIG. 2. The two sides ofnotch 27 in the end of terminal 24 are then deformed over the end ofstring 23 to secure the string in the terminal, as shown in FIG. 1. Thefree end of string 23 may be cut off. The result of such a suspension iseffectively equivalent to an open circuit and will reflect substantiallyall vibrations exactly in phase.

The hook 28 of spring, 21 is secured in a notch 29 in an upwardlyextending flange portion 30 of plate 11. Accordingly, this end of spring21 is rigidly secured to the mass of the plate and is effectivelyequivalent to a short circuit. At this end of spring 21, substantiallyall the vibrations will be reflected with a phase reversal, that is, 180out of phase with the incident vibrations.

A link 33 is used to couple vibrations between springs 20 and 21 atrespective points intermediate the midpoint and the suspended end of thespring. The link includes a pair of clip portions 34 and 35 which clipover the top part of a coil of springs 21 and 20 respectively. The clips34 and 35 extend downwardly from opposite ends and opposite sides of arigid and flexible cross bar 36. Because clips 34 and 35 are on oppositesides of cross bar 36, the coils of springs 21 and 20 to which they areclipped are at different distances from the transducers. distribute thestanding wave pattern for even frequency This helps.

response, and also breaks up the path lengths of travel for reflectedsignals for even reverberation.

Placement of link 33 affects the distribution of standing wave patternsin the system. Of course the further away from the transducers the linkis placed, the longer will be the delay time. The reverberation time isalso affected by the link placement. It is desirable to keep the highfrequency reverberation time as long as possible in relation to the lowbecause there are so many more losses at the higher frequencies than atthe lower frequencies that if this were not done an unnatural soundcould result. The closer toward the suspended ends of the springs thelink is placed, the more the high frequency reverberation time isemphasized. Thu the placement of the link involves a compromise ofseveral factors including the delay time, the high and low frequencyreverberation times, and the optimum distribution of standing wavepatterns for even frequency response.

A reverberation unit should provide a delayed signal of decayingamplitude. The ideal delay line would consist of a vibrationtransmitting member such as a spring having a resonant frequency at thelowest possible number of cycles. Accordingly, the harmonics at whichthe particular spring is resonant will extend through the entire rangeof frequencies desired to be conveyed. Most of the fre quencies desiredto be conveyed will thereby fall at one of the harmonic peaks of thespring to be transmitted thereby at peak efficiency. The length of sucha vibration transmitting member would be selected according to the delaytime desired.

A difliculty with a device of the above type is the fact that thereflections of the vibrations occurring at each end of the spring willbe spaced sufficiently that the arrival time of echos will be audible tothe listener. In other words, a repetitious reproduction of the inputsignal will occur at a diminishing amplitude. To convert such a deviceinto an acceptable reverberation unit, suflicient reflective paths wouldhave to be added to cause the reflections to occur at a rate that wouldmake them indistinguishable. Such a modification can be extremelycomplex and may result in excessive size of the unit.

The reverberation device constructed in accordance with the inventionutilizes a construction wherein the characteristics of a very lowresonant frequency spring are achieved by utilizing two springs of ahigher resonant frequency. Spring 20 is a one-quarter wavelengthresonator because of the freely suspended mounting, while spring 21 is aone-half wavelength resonator because of its grounded or fixed endmounting. Harmonics will occur at odd intervals in spring 20 and evenintervals in spring 21 such that when combined, the harmonic peaks falldirectly in between each other and maintain that relationship. Theresult is an even distribution of resonant harmonic peaks at whichenergy may be transferred, with reinforcement or cancellation occurringdue to the even distribution of peaks. Furthermore, because of the evendistribution of resonant peaks, the minimum energy transfer level isalso raised. By placing coupling link 33 intermediate the ends of thesprings, reflecting paths are created between the link and the suspendedends to provide additional resonant combinations which further fill inthe gaps between the harmonic peaks. This further raises the minimumenergy transfer level at all frequencies. The various combinations ofresonant frequencies and harmonies available thus provide an evenresponse curve for the reverberation unit.

The foregoing device also provides sufficient reflective paths ofdifferent lengths for vibrations so that the arrival of reflectedvibrations is not distinguishable by ear. When an AC. voltage in theaudio frequency range is placed on driver transducer 16, the electricalenergy is converted into torsional vibration in the first helical spring20. The mechanical impedance of the driver transducer is selected to beseveral times lower than the characteristic impedance of the spring 20.As the vibrational wave starts to propagate along the first spring itcan travel along several paths. One path, the primary path, leads fromspring 20 to coupling link 33 back along spring 22 to transducer 17.There the wave will arrive with a delay time which depends upon thedelay characteristic of the spring and its length. The impedance oftransducer 17 is selected to be many times lower than the characteristicimpedance of coil spring 21. Accordingly, only a small fraction of thevibrational energy is converted back into electrical energy while thelargest percentage is reflected. The reflected wave will again travelalong several paths of which one leads along the spring 21 throughcoupling link 33 back along spring 20 to the transducer 16. Here againbecause of the mismatch condition of the impedances, most of thevibrational wave will'be reflected. The vibrational wave will continueto commute between driver and receiver until its energy is fullydissipated by the inherent losses of the system. The time it takes forthese reflected vibrations to decay to a given level is thereverberation time.

The construction of the reverberation unit provides a number of otherpossible paths for vibrational transmission. Because coupling link 33represents a transmission irregularity, it reflects a certain amount ofthe vibrational energy. At the freely suspended end of spring 20, fullreflection of the wave with no phase reversal takes place while at thegrounded end of spring 21, full reflection with a phase reversal occurs.Because of the various places in the spring system at which reflectionsoccur, the multitude of standing wave patterns previously discussed areset up. Together with the initial delay time and the numerous echosproduced by the spring system and its various paths, the output of thereverberation unit is a delayed signal of decaying amplitude closelyresembling the conditions of a concert hall.

Various relationships exist between the dimensions and properties of thesystem components. The fundamental resonance frequency of the springdepends upon the number of turns of wire, diameter of the wire, thediameter of the coil, the density of the material of which the spring ismade, and the modulus of elasticity of the spring. Of all the foregoingparameters, varying the diameter of the coil seems to be the mosteffective way of altering the fundamental frequency of a spring. It willprobably be desirable in the system to damp out all vibrations below 200cycles and above 5,000 cycles. This range has been found satisfactoryfor a proper acoustical effect, although other circumstances may dictatethat a difference range of frequencies be used. The delay time, ofcourse, will be determined by the length of the transmission springbetween input and output transducers, and the reverberation time will beaffected by the Q of the spring. It has been found that tension on thesprings does not affect any measurable parameter, however, it wasnoticed that a springy sound becomes apparent with increased tension onthe spring. The diameter of the spring, and the diameter of the wire,inversely affect the upper cut off frequency. More turns, and a lowercut off frequency of the spring, increases the delay. An increase inwire diameter and an increase in the modulus of elasticity increases thereverberation time. The mass of coupling link 33 inversely affects thehigh frequency response as does the compliance of the coupling link andof the wire of the spring.

It will be apparent that the foregoing described con struction resultsin a considerably improved reverberation device. Because both springsare identical, the device is simplified. .Furthermore, only one inputand one output transducer is necessary and a short physical length for agiven reverberation time is possible. Reinforcements and cancellationsare generally avoided because of the planned placement of the harmonicpeaks of resonance for a smooth response curve throughout the frequencyrange.

Referring now to FIG. 4, the construction of the transducer may be seenin more detail. Both transducers 16 and 17 are constructed alike and aredriven by a ceramic bender or bimorph 41. The impedance of therespective benders may be selected to properly match the impedance ofthe driving and driven electrical circuits. The benders drive a leversystem that converts the bending motion of the ceramic bender into aforce couple. When this force couple acts upon opposite points on thecircumference of the spring it produces a torsional motion. On the otherhand, when a force couple is exerted on the ends of the lever system bytorsional motion of the spring, the ceramic bender is bent to produce anelectrical signal.

The lever system includes a pair of lever arms 42 and 43 which are bentlongitudinally for rigidity. The arms 42, 43 are joined by an integralweb 44, and the ceramic bender 41 passes through an opening in web 44and through openings in the respective lever arms 42 and 43. Thus, theceramic bender engages one end of each of levers 42 and 43, which leversin turn are fulcrumed at the juncture with the integral web 44. Sincethe ceramic bender extends through an opening in web 44, its center isfixed in relation to the fulcrums of respective levers 42 and 43. Epoxycement is used to secure the bender to the levers 42 and 43 and to web44, and also serves to insulate the bender from the metal levers andweb. Wires 48 connect each side of the benders 44 to terminals onterminal board 63, so that input and output signals are conducted to andfrom the respective benders.

In FIG. 5 the lever system is shown schematic-ally for clarity, whereinportion A represents the long portion of lever 42 and portion B the longportion of lever 43. Portion C represents the short portion of lever 42which is engaged by bender 41, while portion D represents the shortportion of lever 43 which is engaged by bender 41. Member E representsthe connecting web 44, and portions F and G represent the juncturesbetween web 44 and levers 42 and 43 respectively. Member H representsthe bender or bimorph 41. It may be seen that as member H bends to the Xposition, the leverage at the ends exerts a force couple at the fulcrumsrepresented by points F and G. This twists member E with the ends ofmembers A and B moving in opposite directions as designated X to set upa force couple. When member H bends to the Y position, similar actioncauses displacement of the ends of A and B as designated Y. Conversely,it may be seen that a force couple applied to the ends of members A andB will cause opposite displacement thereof to displace points C and D inthe same direction with respect to the center of member E. Accordingly,this will bend member H and produce an electrical signal therein. At theends of levers 42 and 43 is a stainless steel U-shaped connecting member46 (FIG. 4). The center portion of U-shaped member 46 is curved slightlyto prevent twisting, and the spring 20 is rigidly cemented therein. Thesides of U-shaped member 46 are respectively connected to the ends oflevers 42 and 43 by cementing projections in openings in the levers. Theresult is a resilient extension of the levers which offers maximumstiffness to the force couple being transmitted to or from spring 20,but which offers minimum resistance or stiffness to outside vibrationsfor damping the same.

A damping rubber cylinder 45 is placed between the two levers 42 and 43in order to introduce maximum damping to flexural vibrations of thelever arms while having a negligible affect on the torsional motionthereof.

FIG. 4a shows an alternative coupling between levers 42, 43 and spring20. A nylon bearing 51 extends between the levers 42 and 43 and spring20 is hooked about bearing 51 in a groove about the circumferencethereof. In either the case of FIG. 4 or the case of FIG. 4a thecompliance of the lever arms, together with the combined masses of thebearing 51 or member 46 and the hook of the spring are adjusted toresonate at a frequency near the upper cut off frequency of the entiresystem. This supplements the response curve of the system, whichnormally declines at this point, to provide a sharper response cut offat the upper cut off frequency.

The transducer units 16 and 17 are mounted in univers-al joints topresent high damping to all vibrations except the torsional mode set upby the transducers themselves. This mounting is shown in FIGS. 6 through8. The integral stamping of levers 42 and 43 and connecting web 44 isprovided with a pair of mounting ears 53 and 54. These ears are cementedinto notches 55 and 55, respectively, of a lead block 57, and areflexible so that the lever system may pivot in a horizontal plane withrespect to the block. Lead is used for the block because its elasticityis negligible and therefore cannot transmit any vibration, isolatingcross talk between the input and output transducers. Each of blocks 57are pivot-ally mounted on a horizontal pin 58 by means of a dampingrubber insert 59. The mass of the block together with the damping rubberinsert is a low pass filter which provides the low frequency cut off ofthe transducer. The resistive component of the rubber introduces lossbelow the cut off frequency. Because mounting ears 53 and 54 areflexible, and because the blocks 57 are pivotal, the transducer isprovided with a high loss universal hinge which allows the transducer tomove freely in two planes and at the same time introduces sufficientloss to damp out low frequency flexural waves in the springs. This isvery significant in damping out vibrations caused by outside sources.

The transducers are mounted on plate 11 as follows. Pin 58 is mounted ina U-shaped'flange 61 formed out of a mounting plate 62 secured tosupport plate 11. An insulating board 63 is mounted between plate 62 andplate 11 and may carry the terminals for the electrical connections tothe respective ceramic bimorphs 41. The outer housing may be mounted bymeans of springs or damping pads, etc., to further reduce the effect ofoutside vibrations and to protect the system.

Referring to FIG. 9 a simplified schematic diagram of a circuit is shownin which a reverberation unit of the type described may be used. Asource of audio frequency signals 71 is coupled through a preamplifier'72, through an amplifier '73, and from there to a speaker 74,

' where they are audibly reproduced. Some of the output of amplifier 73is fed through a further amplifier '75 for driving a reverberation unit76 of the type described. Output signals from the reverberation unit 76are then fed back to the amplifier 73 so that they may be reproduced byspeaker 74. By including signals of delayed decaying amplitude in thereproduced sound, a concert hall effect is created. This results fromadding to the sound reaching the listeners ears, reflected and delayedsound waves which would normally be present in a large auditorium orconcert hall.

From the foregoing description it may be seen that the inventionprovides an improved device for producing delayed decaying electricalsignals which is low in cost and simple of construction. The deviceproduces sufiicient reflections to render them indistinguishable by earand is insensitive to outside vibration. The transducer which drives thedevice is an efficient unit which produces torsional vibrations fordriving the springs in the reverberation device, and the identicalreceiver transducer which converts torsional vibrations of the springsinto electrical signals is similarly efficient.

I claim:

1. A transducer device adapted to transform between electrical signalsand a vibrating body operating in the torsional mode, including incombination, a pair' of spaced levers each with first and second endsand each having a fulcrum intermediate said ends thereof, said firstends each adapted to be joined to the vibrating body and to move aboutsaid respective fulcrums associated therewith in opposite directionsrelative to each other, and a bimorph joined to said second ends of saidlevers and .adapted to be coupled to an electrical circuit for trans-:forming in a bending mode between electrical signals and mechanicalmotion. Y

2. The transducer of claim 1 wherein said bimorph has an intermediateregion fixed with respect to said fulcrums of said levers, said bimorphtransforming between electrical signals and mechanical motion inopposite directions about said region.

3. A transducer device adapted to transform between electrical signalsand a vibrating body operating in the torsional mode, including incombination, first and second levers each having first and secondadjoining arm portions forming a bell crank like structure and includinga fulcrum at the juncture of said arm portions, means positioning saidfulcrums relative to one another, said second arm portions each adaptedto be joined to the vibrating body and to move about said fulcrumassociated therewith in opposite directions relative to each other, abimorph connected to the first arm portion of said first lever on oneside of said fulcrum associated therewith and to the like arm portionofsaid second lever on the side of said fulcrum associated therewithopposite from said one side, said bimorph having a center fixed withrespect to said fulcrum, and means for electrical connection to saidbimorph, said bimorph being responsive to an electrical signal to bendthereby applying a force couple to each of said first arm portions ofsaid levers lo move said second arm portions thereof about said fulcrumsin opposite directions relative to each other, and said himorph furtherbeing responsive to displacement of said second arm portions withrespect to said fulcrums associated therewith to produce electricalsignals.

4. A transducer device for producing torsional motion from electricalsignals and electrical signals from torsional motion including incombination, a pair of elongated levers disposed adjacent one another,each of said levers having a first end and a second end and a fulcrumintermediate the same and fixed in relation to the fulcrum of the otherof said levers, means at said first ends of said levers and responsiveto electrical signals applied thereto to displace said first ends, saidmeans further being responsive to displacement of said first ends toproduce electrical signals, said levers being disposed such that thesecond ends thereof move in opposite directions to produce torsionalmovement upon displacement of said first ends, and such thatdisplacement of said second ends in opposite directions due to torsionalmovement causes displacement of said first ends to cause said means toproduce electrical signals.

5. The transducer device of claim 4 wherein said means at said firstends of said levers includes a bimorph having a point intermediate theends thereof fixed in relation to the fulcrums of said levers.

6. A transducer device for producing torsional motion from electricalsignals and electrical signals from torsional motion, including incombination, a pair of elongated levers disposed adjacent one another,each of said levers having a first end and a second end and a fulcrumintermediate the same, 'an integral web portion connecting said fulcrumssuch that they are fixed in relation to each other, an elongated bimorphwith the respective ends thereof engaging said first ends of saidlevers, said bimorph extending through an opening in said web portionand'having a point intermediate-its ends fixedly engaging said webportion, said bimorph being responsive to electrical signals appliedthereto to bend and displace said first ends of said levers in relationto said web portion and hence to the fulcrums of said levers, saidbimorph further being responsive to displacement of said first ends withrespect to said web portion and the fulcrums of said levers to produceelectrical signals, said levers being disposed such that the second endsthereof move in opposite directions to produce torsional movement upondisplacement of said first ends, and such that displacement of saidsecond ends in opposite directions due to torsional movement causesdisplacement of said first ends.

7. The transducer device of claim 6 further including a U-shaped linkhaving a pair of free sides fixed to respective ones of said levers atthe first ends thereof and having a center portion and means thereon forcoupling said center portion to a vibration transmitting member.

8. The transducer device of claim 6 further including a ridged bearingmember extending between said first ends of said first and second leversto be angularly displaced thereby, and means intermediate the ends ofsaid bearing member for coupling to a vibration transmitting member.

9. The transducer device of claim 6 further including a lead mountingblock and means pivotally mounting the same, and flexible ears extendingfrom said Web portion between said levers, said ears being mounted insaid lead block such that said levers and integral Web portion arepivotal with respect to said lead block about an axis 15 transverse tothe pivotal axis of said lead blocks, said mounting thereby providinguniversal motion for said transducer device to damp all but torsionalvibrations therein.

References Cited by the Examiner UNITED STATES PATENTS 2,513,326 7/1950Bauer 179-10041 2,565,586 8/1951 Bauer 3108.6 2,671,178 3/1954 Tomcik3l08.5

MILTON O. HIRSHFIELD, Primary Examiner. A. J. ROSSI, .T. D. MILLER,Assistant Examiners.

1. A TRANSDUCER DEVICE ADAPTED TO TRANSFORM BETWEEN ELECTRICAL SIGNALSAND A VIBRATING BODY OPERATING IN THE TORSIONAL MODE, INCLUDING INCOMBINATION, A PAIR OF SPACED LEVERS EACH WITH FIRST AND SECOND ENDS ANDEACH HAVING A FULCRUM INTERMEDIATE SAID ENDS THEREOF, SAID FIRST ENDSEACH ADAPTED TO BE JOINED TO THE VIBRATING BODY AND TO MOVE ABOUT SAIDRESPECTIVE FULCRUMS ASSOCIATED THEREWITH IN OPPOSITE DIRECTIONS RELATIVETO EACH OTHER, AND A BIMORPH JOINED TO SAID SECOND ENDS OF SAID LEVERSAND ADAPTED TO BE COUPLED TO AN ELECTRICAL CIRCUIT FOR TRANSFORMING IN ABENDING MODE BETWEEN ELECTRICAL SIGNALS AND MECHANICAL MOTION.